The Squeak community had many discussions in the past on Namespaces within the standard image. Especially after other Smalltalks like VisualWorks provide Namespace by default.
The easy way is to have conventions so the names just don't overlap.
There have been proposals like the one from Göran (and working implementations) for namespace support.
One idea is to reify the prefixes so you could write My::Class instead of MyClass.
Smalltalk/MT uses the same notation. However, no proposal for Squeak has been adopted yet.
Michael van der Gulik has now released a premade Namespaced image. This is part of his SecureSqueak project.
There is also a video available.